Cytomegalovirus

By Laura Freeman

Published: August 17, 2017

Karen Fowler, Dr. PH

The pregnancy risk women don't know to avoid

Pregnant women take vitamins to avoid neural tube defects such as spina bifida. They avoid drinking to prevent fetal alcohol syndrome, and if Down's syndrome is a concern, they may have amniocentesis. But only 10 percent know that finishing their toddler's cookie could put them at risk for contracting a virus that causes more long-term problems and childhood deaths than any of the above.

By age 40, 60 percent or more of the US population has contracted cytomegalovirus (CMV) at some point in their lives. If this happens to women when they are pregnant, or if they are infected by a new strain or have a recurrence at that critical time, their child is at risk of being born with congenital CMV.

For an adult or a child, a CMV infection might not even be noticed, or they may just feel like they have a cold. But for a baby who contracts it in the womb, congenital CMV can be devastating. It is the largest nongenetic cause of sensory loss and mental disabilities in children.

"On average, one out of 150 babies in the United States is born with a congenital CMV infection," Karen Fowler, Dr. PH said. "10 to 15 percent of those children will develop significant problems. The most common risk is deafness, but children may also have neuromuscular and developmental deficits, vision problems, small head size and seizures. Those most affected may die before they are born.

"We don't know yet why some children exposed to the virus show no noticeable harmful effects while others suffer profound problems. That's one of the questions we are working to answer

Exposure any time during pregnancy can affect the fetus, but there are some indications that the most profound cases tend to occur when exposure happens early in pregnancy during critical stages of brain and organ development.

As a part of the investigative team at what is arguably the world's most highly regarded CMV research program, Fowler is well placed to find those answers. At Children's of Alabama and UAB, she and her fellow researchers, , MD; William Britt, MD; Shannon Ross, MD; , MD are following in the footsteps of CMV pioneers who have been making breakthroughs against the virus for the past 50 years.

A major recent contribution by Fowler and Boppana is a screening test that can quickly detect with 97 percent accuracy whether an infant has a congenital CMV infection. In the past, testing with cultures took time and was rarely done unless pediatricians had reason to suspect the infection. About 90 percent of infected infants are asymptomatic at birth but may develop late onset hearing loss that may not be detected until it has already begun to interfere with language skills.

"It would be wonderful if screening for CMV could be available to all babies at birth," Fowler said. "If we know about the infection we can treat it promptly with an antiviral which can make a difference in the outcome. Our researchers have shown that ganciclovir can improve hearing, and by extending treatment from six weeks to six months, we can extend improvements for 24 months or more."

A new study is looking at whether the oral drug valganciclovir will show similar benefits in improving outcomes.

"We hope to eventually find a vaccine that we can give women before they become pregnant so they won't be infected or pass the infection to their babies," Fowler said.

Tests are available to determine whether a patient has had CMV in the past, but women should not deliberately contract a CMV infection hoping to acquire antibodies before they become pregnant. There are multiple strains of the virus, and even if they are immune to one strain, they can still become reinfected with another.

"CMV is transmitted by body fluids--saliva, urine and sexual contact," Fowler said. "Having another child at home or working closely with children can increase the risks of transmission.

"We recommend that pregnant women be extra vigilant about hand washing and using hand sanitizers, particularly when they are around small children, after changing diapers or picking up toys or other things that might have had mouth contact. That includes not eating leftovers or using the same utensils. Goodnight kisses should be okay--but on the forehead, not the mouth.

"Sometimes, even with the best efforts, infections can happen, but women say that knowing about CMV gives them something they can do to try to avoid it and to have the peace of knowing they did their best."